The medical profession is frequently confronted with cases of cardiogenic shock (i.e. a condition in which the heart still functions but is not pumping sufficient blood to keep the patient alive). Emergency treatment of this condition often requires some form of cardiac assist which maintains a blood flow sufficient for survival while other measures are initiated to restore the heart itself to more normal function.
At the present time, the only methods available for a cardiac assist of this nature are pump systems whose connection to the vascular system involves major surgery, or a balloon catheter inserted into an appropriate artery. Unfortunately, major surgery may involve too much delay or risk for a patient in cardiogenic shock, and the balloon catheter may not provide sufficient improvement in cardiac output.
It has been proposed to provide left-sided circulatory support by the use of non-thoracotomy vascular access. In such systems, two simultaneous arterial sites would be employed to pump blood from the heart into the arterial system. However, this technique would necessitate the use of long, small-bore cannulae which would result in large pressure drops. Exposure of conduits with negative pressure could result in air embolism and serious complications. In addition, the subclavian artery would need to be employed for the pump inlet because of its proximity to the heart. Surgical access to this vessel is more difficult than for the femoral artery.
Use of an external pump for support of the right heart would require access at two simultaneous venous sites. In this case the pump output would need to be returned by a long, small-bore cannula to the pulmonary artery. Similar complications of large pressure drops with negative pressures and possible air embolism could occur. The prior art has thus been unable to provide an easily-implemented low-risk circulatory-assist device capable of rapidly providing full flow heart assist to critically ill patients.